The invention relates generally to fluid vaporizing devices such as aerosol generators, having a controlled temperature profile capillary passageway with electrical leads and fluid connections all located toward an inlet end of the device.
Devices for generating aerosols include devices for administering medicaments to patients such as those disclosed in U.S. Pat. Nos. 4,811,731 and 4,627,432. In the disclosed devices for administering medicaments, a capsule is pierced by a pin to release a medicament in powered form. A user then inhales the released medicament through an opening in the device. While such devices may be acceptable for use in delivering medicaments in powered form, they are not suitable for delivering medicaments in liquid form. Such devices are also not well suited to deliver medicaments to persons who might have difficulty in generating a sufficient flow of air through the device to properly inhale the medicaments, such as asthma sufferers.
Another well known technique for generating an aerosol involves the use of a manually operated pump, which draws liquid from a reservoir and forces it through a small nozzle opening to form a fine spray. A disadvantage of such aerosol generators, at least in medicament delivery applications, is the difficulty of properly synchronizing inhalation with pumping. More importantly, however, because such aerosol generators tend to produce particles of large size, their use as inhalers is compromised because large particles tend to not penetrate deeply enough into the lungs.
Another popular technique for generating an aerosol including liquid or powder particles involves the use of a compressed propellant, often containing a chloro-fluoro-carbon (CFC) or hydro-fluoro-alkane (HFA) to entrain a material. The use of compressed propellants can be inefficient in converting the medicament or formulation into a respirable aerosol. Aerosols generated by propellant-based arrangements generally have particles that are either too large or traveling at too high a velocity to ensure deep lung penetration. The HFAs, in particular can (at least in some cases) produce aerosols in short, high velocity bursts. Because of this high velocity, much of the aerosol is not respirable and is deposited in the oropharyngeal region rather than deep in the lungs where preferred.
An exemplary embodiment of a fluid vaporizing device according to the invention comprises two concentric, electrically conductive tubes, the tubes being electrically and physically connected near a distal or output end of said tubes, and the tubes each having electrical connections to a power source, with the electrical connections to a power source being near a proximal or inlet end of the tubes. The inlet end of the inner one of the concentric tubes is in fluid communication with a source of fluid. An air gap is provided between the inner and outer tubes, and electrical current is passed through the outer tube, through a brazed or welded connection between the outer and inner tubes near the distal ends of the tubes, and through the inner tube.
Another exemplary embodiment of the fluid vaporizing device according to the invention comprises a reservoir containing a liquid, and a flow passage in fluid communication with the reservoir. The device also comprises a capillary passage in fluid communication with the reservoir, and a heater arranged relative to the capillary passage so as to heat at least a portion of the capillary passage sufficiently to volatilize liquid contained in the portion of the capillary passage.